Designing Analysis Of Reinforced Concrete Grid-Beams Structures

The one-way slab, two-way slabs, principal and subordinate-beam structure, non-beam structure and the grid-beam structure are putting into use in the reinforced concrete slab. When the ratio of two spans on the surface size of a floor slab is less than 2, it is appropriate to adopt the grid-beams as the floor form structure. Under this situation, the beams and slabs will exert their advantages respectively. And it is common in the public buildings. In thisarticle, Grid-beam structure by simply supported on foursides in the engineering is discussed.Its calculated method of internal force and displacement under uniform load and choosingsection to control the wide of crack is studied also.According to the assumed displacement function: w(x.y) = Dcos x/a-cos y/b, determine the displacement function by using the principle of potential energy, and calculated formula of displacement ,moment and shear of every beam in the grid-beam structure is offered. And it is simple and useful. The maximum relative errors of calculation compare with the results of literature[3] are less than 10%, commonly the errors are still less than 5%. The accuracy of deflection is higher. The problem of determining the grid-beam is discussed also. It is one of the key problems of the structure designing to determining the safe, economic and reasonable section. The one of key problems for using load to evaluation displacement is to determine its stiffness. As there are many factors that affect the stiffness of the concrete beam. And some less important factors are omitted. Some load assumptions are used and through suitable simplification, that make the section stiffness only has the relation with section stiffness and reinforcement rate. It is suitable to apply by making table. The formula of the grid-beam section is deduced according to the displacement of the beam. Not only the load is considered, but also the distance, the span, the wide and the percent of the reinforcement is considered. The chosen section is also meeted the stiffness. In ordinary circumstances, the height of the grid-beam is about the 1/16 of the short span. And thesection is decided by the stiffness.According to the crack wide of the norm, the relationship of the diameter and the rate of the reinforcement are made up. It is suitable for designing to choose the largest diameter of the reinforce steel to meet the wide of crack by using the table of the rate of the reinforce steel. The internal force, displacement, crack, and the section of the grid-beam are discussed wholly. The application of this method is illustrated by some example and construction case and the precision is analyzed and compared, which apply a feasible method for designing this kind of structure. The method that discussed here is also suitable for joist floors. The theory basis is applied for understanding the inner load, displacement, and its varying regulation of the structure. It also has some reference significance for analyzing the internal force of crossing basement and its similar structures.